The owner of a home-built submarine has told investigators that a missing female Swedish journalist died aboard in an accident, and he buried her at sea in an unspecified location, police in Copenhagen say.

Peter Madsen will continue to be held on preliminary manslaughter charges, police said Monday, declining to give more details.

Kim Wall, a 30-year-old journalist reported to be aboard Madsen's submarine UC3 Nautilus on an assignment, disappeared more than a week ago. Madsen has denied any wrongdoing.

Wall's family previously told The Associated Press that Kim worked in many dangerous places as a journalist, but it was unimaginable that "something could happen… just a few miles from the childhood home."

Kim Wall, shown in a 2015 handout photo, was working on a profile of amateur submarine builder Peter Madsen when she died. (Tom Wall/Associated Press)